There are a number of air-filled cavities called sinuses in the skull (Stedman's Medical Dictionary, 27th Edition, page 1644, (1999), Lippincott Williams & Wilkins, Baltimore, Md.). Four pairs of sinuses known as the paranasal sinuses, connect the space (known as the nasal passage) running from the nostrils and up through the nose. These four pairs of paranasal sinuses are the frontal sinuses, the maxillary sinuses, the ethmoid sinuses, and the sphenoid sinuses. They are located, respectively, in the forehead, behind the cheekbones, between the eyes, and behind the eyes. A membrane lining the sinuses secretes mucus, which drains into the nasal passage from a small channel in each sinus. Healthy sinuses are sterile and contain no bacteria. In contrast, the nasal passage, normally contains many bacteria that enter through the nostrils as a person breathes.
A number of factors and/or processes are involved in maintaining healthy sinuses. The mucus secreted by the membrane lining must be fluid but sticky, in order to flow freely yet absorb pollutants and entrap bacteria. It must also contain sufficient amounts of bacteria-fighting substances, such as antibodies. Additionally, small hair-like projections called cilia, located in the nostril, must beat in unison to propel mucus outward, in order to expel bacteria and other particles. Moreover, the mucous membranes themselves must be intact, and the sinus passages must be open to allow drainage and the circulation of air through the nasal passage. When one or more of these processes or factors are amiss, causing obstruction of the sinus passage, an infection called sinusitis develops.
Sinusitis is an inflammation of the membrane lining one or more paranasal sinuses. There are three different types of sinusitis: acute, recurrent acute, and chronic. Acute sinusitis is characterized as lasting less than three weeks or occurring less than four times a year. Acute sinusitis can be successfully treated using antibiotics, leaving no damage to the linings of the sinus tissue. Recurrent acute sinusitis occurs more often but leaves no significant damage. Chronic sinusitis lasts longer than three weeks and often continues for months. In cases of chronic sinusitis, there is usually tissue damage. According to the Center for Disease Control (CDC), thirty seven million cases of chronic sinusitis are reported annually.
Causes of Sinusitis
The most common cause for sinusitis is a viral cold or flu that infects the upper respiratory tract and causes obstruction. Obstruction creates an environment that is hospitable for bacteria, the primary cause of acute sinusitis (Etkins et al., 1999 Nidus Information Services, Inc. Well-Connected Report: Sinusitis. June 1999. (Online) www.well-connected.com.). The bacteria most commonly found in acute sinusitis are Streptococcus pneumoniae (also called pneumococcal pneumonia or pneumococci), H. influenzae (a common bacteria associated with many respiratory infections in young children), and Moraxella (or Branhamella) catarrhalis. Less common bacterial culprits include other streptococcal strains including Staphylococcus aureus. 
Fungi are an uncommon cause of sinusitis, but its incidence is increasing. The fungus Aspergillus is the common cause of fungal sinusitis. Others include Curvularia, Bipolaris, Exserohilum, and Mucormycosis. Fungal infections can be very serious and should be suspected in people with sinusitis who also have diabetes, leukemia, AIDS, or other conditions that impair the immune systems. Fungal infections can also occur in patients with healthy immune systems. There have been a few reports of fungal sinusitis caused by Metarrhizium anisopliae which is used in biological insect control.
Chronic or recurrent acute sinusitis can be a lifelong condition and may result from untreated acute sinusitis that causes damage to the mucous membranes, medical disorders that cause chronic thickened stagnant mucus, or abnormalities in the nasal passage such as polyps, enlarged adenoids, cleft palate, or tumors. The same organisms that cause acute sinusitis are often present in chronic sinusitis. In addition, about 20% of chronic sinusitis cases (Etkins et al., 1999, Id.) are caused by Staphylococcus aureus (commonly called Staph infection). Along with these bacteria, certain anaerobic bacteria, particularly the species Peptostreptococcus, Fusobacterium, and Prevotella, are found in 88% of cultures in chronic sinusitis cases (Etkins et al., 1999, Id.). Fungi can also cause chronic and recurrent sinusitis. An uncommon form of chronic and highly recurrent sinusitis is caused by an allergic reaction to fungi, usually, aspergillus, growing in the sinus cavities. Fungal sinusitis usually occurs in younger people with healthy immune systems and is more likely to be found in warm climates.
Symptoms of Sinusitis
In acute sinusitis, symptoms almost always present are nasal congestion and discharge which is typically thick and contains pus that is yellowish to yellow-green. Severe headache occurs, and there is pain in the face. A persistent cough occurs particularly during the day. Other upper respiratory symptoms and fever may be present. Sneezing, sore throat, muscle aches, and fatigue are rarely caused by sinusitis itself, but may result from symptoms or causes, such as muscle aches caused by fever, sore throat caused by post-nasal drip, and sneezing resulting from allergies.
The symptoms of recurrent acute and chronic sinusitis tend to be vague and generalized, last longer than eight weeks, and occur throughout the year, even during nonallergy seasons. Nasal congestion and obstruction are common. Yellowish discharge, chronic cough, bad breath, and postnasal drip may occur. Sufferers do not usually experience facial pain unless the infection is in the frontal sinuses, which results in a dull, constant ache. However, facial tenderness or pressure may be present.
Site-specific symptoms depend on the location of the infection. Frontal sinusitis causes pain across the lower forehead. Maxillary sinusitis causes pain over the cheeks and may travel to the teeth, and the hard palate in the mouth sometimes becomes swollen. Ethmoid sinusitis causes pain behind the eyes and sometimes redness and tenderness in the area across the top of the nose. Sphenoid sinusitis rarely occurs by itself. When it does, the pain may be experienced behind the eyes, across the forehead, or in the face. Rare complications of sinusitis can produce additional symptoms which may be severe or even life threatening.
Treatments of Sinusitis
The primary objectives for treatment of sinusitis are reduction of swelling, eradication of infection, draining of the sinuses, and ensuring that the sinuses remain open. Less than half of patients reporting symptoms of sinusitis need aggressive treatment and can be cured using home remedies and decongestants alone. Steam inhalation and warm compresses applied over the sinus are often sufficient to relieve discomfort. Many over-the-counter decongestants are available, either in tablet form or as sprays, drops, or vapors, which bring the medication into direct contact with nasal tissue.
Antibiotics are prescribed if decongestants fail to relieve symptoms or if other problems exist, including signs of infection (such as yellowish nasal discharge). They prevent complications, relieve symptoms, and reduce the risk of chronic sinusitis. Most patients with sinusitis caused by bacteria can be successfully treated with antibiotics used along with a nasal or oral decongestant.
Chronic sinusitis is often difficult to treat successfully, however, as some symptoms persist even after prolonged courses of antibiotics. The usefulness of antibiotics in treating chronic sinusitis is debated. Steroid nasal sprays are commonly used to treat inflammation in chronic sinusitis. For patients with severe chronic sinusitis, a doctor may prescribe steroids, such as prednisone. Since oral steroids can have serious side effects, they are prescribed only when other medications have not been effective.
When medical treatment fails, surgery may be the only alternative in treating chronic sinusitis. Studies suggest that the most patients who undergo surgery have fewer symptoms and better life. Presently, the most common surgery done is functional endoscopic sinus surgery, in which the diseased and thickened tissues from the sinuses are removed to allow drainage. This type of surgery is less invasive than conventional sinus surgery, and serious complications are rare.
Considerations and Concerns of Treatments
Sprays, drops, and vapors work quickly but often require frequent administration. Nasal decongestants may dry out the affected areas and damage tissues. With prolonged use, nasal decongestants become ineffective. The tendency is to then increase the frequency of use to as often as once an hour. Withdrawal from the drugs after three to five days of over-frequent use can itself cause symptoms of sinusitis and the return of nasal congestion phenomenon known as rebound effect. Short-acting nasal decongestants may cause rebound effect after only eight hours. Rebound effect leads to dependency when the patient takes the decongestant to treat the rebound effect, the drug becomes ineffective, the patient withdraws, and the condition rebounds again, with the nasal passages becoming swollen and burning. Eventually, the condition can become worse than before the medication was taken. Nasal decongestants are generally recommended for no more than one to three days of use because of this risk.
Some oral decongestants may cause constriction of other vessels in the body, temporarily raising blood pressure in people with hypertension. Other side effects of oral decongestants include insomnia, agitation, abnormal heart rhythms (particularly in people with existing cardiac problems), and urinary retention in men with enlarged prostates. Decongestant sprays and drops, too, are absorbed into the body and can sometimes cause these side effects.
The most common side effect for nearly all antibiotics is gastrointestinal distress. Antibiotics also double the risk for vaginal infections in women. Certain drugs, including some over-the-counter medications, interact with antibiotics, and all antibiotics carry the risk for allergic reactions, which can be serious in some cases. Thus, patients should inform their physician of all medications they are taking and of any drug allergies.
Oral antibiotics are usually prescribed for 7 to 10 days. Patients must take all of the tablets prescribed; failure to do so may increase the risk for reinfection and also for development of antibiotic-resistant bacteria. It should be noted, however, that even after antibiotic treatments, between 10% and 25% of patients still complain of symptoms.
Of major concern to physicians and the public is the emergence of bacterial strains that have become resistant to common antibiotics due to frequent exposure. It should be noted that the average person is not yet endangered by this problem. The risk is greatest in hospitals and nursing homes, but it is still not high. Nonetheless, the prevalence of such antibiotic-resistant bacteria has increased dramatically worldwide, and caution should be exercised.
Nebulization Therapy
Nebulization is a conventional treatment for pulmonary infections related to cystic fibrosis, because it is relatively easy and safe to use, and because it delivers antibiotics topically to the site of infection, with little systemic absorption of the antibiotics. Nebulization has also been known to have been used for sinus infections and pulmonary infections, related to bronchiectasis. Thus, there are few systemic side effects.
Small Aerosolized Particles for Treating Sinusitis
Yokota et al., Japanese Journal of Antibiotics 609(15):48 (1995) reports administration of cefmenoxime using a nebulizer to treat sinusitis patients. These authors evaluated cefmenoxime against clinical isolates from sinusitis patients, and found that minimum inhibitory concentrations were lower when a one percent (1%) solution was used with a nebulizer. The paper speculates that sufficient concentrations exceeding such minimum inhibitory concentrations would be obtained by nebulizer treatment using a cefmenoxime nasal solution.
Guevara et al., Anales O.R.L. Iber.-Amer. XVIII, 3:231–238 (1991), describes aerosol therapy for treating patients suffering from chronic sinusitis. The disclosed aerosol therapy involves delivery of a therapeutic composition comprising 500 mg of Cefotaxime, 5 mg methylprednisolone, and 1.5 ml N-acetylcysteina using an air-jet nebulizer for 15–20 minutes, every 8 hours, over a total period of 15 days. The air-jet nebulizer produces aerodynamic particle diameters of average mass of four microns. Guevara et al. reports a success rate of 96%. However, Guevara et al. does not disclose adding a surfactant to assist deposition, penetration, and retention of the antibiotic in the sinuses. It is also noted that the aerosol therapy of Guevara et al. requires frequent treatments over a long period of time.
Kondo et al., Acta Otolaryngol. Suppl. 525:64–67 (1996), reports treatment of paranasal sinusitis using fosfomycin (FOM) aerosol. Kondo et al. describes delivery of 4 ml of 3% FOM solution using either a jet-type nebulizer or a ultrasonic nebulizer. The jet-type nebulizer produces aerosol particles having about 0.5 to 0.7 μm in diameter, while the ultrasonic-type nebulizer produces particles having about 2–4 μm in diameter. The results of Kondo et al. indicate that the ultrasonic-type nebulizer delivers a higher concentration of FOM to the maxillary sinus surface and is therefore more effective in treating paranasal sinusitis than the jet-type nebulizer. Although Kondo et al. suggests that the preferred aerosol particle size is about 2–4 μm in diameter for deposition of a higher level of antibiotic in the maxillary sinus, Kondo et al. does not disclose an administration schedule or the addition of a surfactant to the FOM solution to further increase the deposition of FOM in the sinuses.
Small Aerosolized Particles for Pulmonary Treatment
Smith et al., U.S. Pat. No. 5,508,269, discloses the use of aminoglycoside aerosol formulations to treat patients suffering from endobronchial infection. Smith et al. describes delivery of the aminoglycoside formulation using a jet or ultrasonic nebulizer that produces aerosol particle size between 1 and 5 μm. The formulation comprises 200 to 400 mg of aminoglycoside dissolved in about 5 ml of solution containing 0.225% sodium chloride and it has a pH between 5.5 to 6.5. Although Smith teaches delivery of aminoglycoside to the endobronchial space using a nebulizer for the treatment endobronchial infection, Smith does not teach an aerosol formulation for treatment of sinusitis and does not disclose a treatment schedule. It is also noted that the aerosol particle size disclosed in Smith et al. is a broad range. It is not predictable what fraction of the aerosol particles between 1 to 5 μm will deposit in the sinuses, and what fraction of the aerosol particles will have a diameter of 1 μm, 2 μm, etc.
Rubin et al., U.S. Pat. No. 5,925,334, describes the use of aerosolized surfactant to promote pulmonary airway clearance. The method of Rubin et al. comprises administering a formulation containing a surfactant using a PARI LC Jet nebulizer for 15 minutes, 3 times a day for 14 consecutive days, to patients suffering from bronchitis or cystic fibrosis. However, Rubin does not teach the use of aerosolized antibiotic or aerosolized antibiotic and surfactant combination to treat sinusitis.
Schmitt et al., U.S. Pat. No. 4,950,477, teaches a method of preventing and treating pulmonary infection by fungi using aerosolized polyenes. The method comprises administering to a patient suffering from pulmonary infection by Asperigillus about 0.01 mg/kg to 6.0 mg/kg of a polyene in an aerosol of particles having an aerodynamic diameter between about 0.5 μm to about 8 μm. Schmitt et al. specifically discloses the administration of amphotericin B. Although Schmitt et al. teaches aerosolized polyenes for treatment of pulmonary infection, Schmitt et al. does not provide guidance for using aerosolized polyenes for treating sinusitis.
O'Riordan et al., Journal of Aerosol Medicine, 20(I):13–23 (1997), reports the effect of nebulizer configuration on delivery of aerosolized tobramycin to the lung. O'Riordan et al. discloses the delivery of tobramycin using either an ultrasonic nebulizer delivering aerosol particles having between 1.45 to 4.3 μm or a jet nebulizer delivering aerosol particles having between 1.25 μm. The results of O'Riordan et al. show that nebulizer configuration affects both the amount of aerosolized tobramycin inhaled as well as the particle size. Specifically, nebulizers that produce large particles are prone to considerable deposition on tubing and connections. O'Riordan et al. recommends that nebulizer configuration be specified in treatment protocols.
Large Particle Aerosolization
In contrast to the references discussed above, Negley et al., ENT Journal, 78(8):550–554 (1999), and Desrosiers et al., (presented at the ENT Academy Meeting, May 1999) teach large particle nebulization therapy for treatment of sinusitis. Negley observes that deposition of medication into the sinuses is best achieved when the aerosolized particles are 16 to 25 μm in size. Desrosiers et al. reports that large particle saline aerosol therapy alone is effective in treating refractory sinusitis and that the addition of tobramycin to the saline solution had minimal benefit.
The journal articles and patents discussed above teach various aerosol therapies for the treatment of sinusitis. However, there does not appear to be agreement among the various authors as to the optimal size or size distribution of the aerosolized particles or even whether antibiotics are effective in treating sinusitis. What has been needed is a clinically effective anti-infective treatment protocol for sinusitis, a more optimal therapy schedule, and an appropriate nebulizer configuration for the deposition of aerosolized anti-infective particles into the sinuses for the successful and consistent treatment of chronic sinusitis.